Disc spring



FIG. 1 is a perspective view of a disc spring in accordance with my newdesign disclosed herein;

FIG. 2 is a front view thereof;

FIG. 3 is a back view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a left side view thereof;

FIG. 6 is a top view thereof; and,

FIG. 7 is a bottom view thereof.

CLAIM The ornamental design for a disc spring, as shown and described.